Analysis of lamotrigine and its metabolites in human plasma and urine by micellar electrokinetic capillary chromatography

A reliable micellar electrokinetic capillary chromatographic method was developed and validated for the determination of lamotrigine and its metabolites in human plasma and urine. The variation of different parameters, such as pH of the background elec trolyte (BGE) and Sodium dodecyl sulfate (SDS) concentration, were evaluated in order to find optimal conditions. Best separation of the analytes was achieved using a BGE composed of 10 mm borate and 50 mm SIDS, pH 9.5; melatonin was selected as the internal standard. Isolation of larnotrigine and its metabolites from plasma and urine was accomplished with an original solid-phase extraction procedure using hydrophiliclypophilic balance cartridges. Good absolute recovery data and satisfactory precision values were obtained. The calibration plots for larnotrigine and its metabolites were linear over the 1-20 mug/mL concentration range. Sensitivity was satisfactory; the limits of detection and quantitation of larnotrigine were 500 ng/mL and 1 mug/mL, respectively. The application of the method to real plasma samples from epileptic patients under therapy with larnotrigine gave good results in terms of accuracy and selectivity, and in agreement with those obtained with an high-performance liquid chromatography (HPLC) method.*